What does an amber OVERSPEED light on the APU panel indicate?

What does an amber OVERSPEED light on the APU panel indicate?

• A. the overspeed shutdown protection feature has failed a self-test or detected an overspeed
• B. the engine is starting normally
• C. the oil temperature is high
• D. the start valve is open

Answer: (B)

An amber OVERSPEED light is a caution for the APU’s overspeed protection system. It comes on to warn that the APU has either detected an RPM that could exceed the safe limit or the overspeed protection logic has failed its self-test. In either case, it signals a non-normal condition that could trigger protective action, such as shutdown, if not addressed. It is not a normal indication of starting, nor is it related to oil temperature or the start valve status. Those conditions would be indicated by different indicators.

An amber OVERSPEED light is a caution for the APU’s overspeed protection system. It comes on to warn that the APU has either detected an RPM that could exceed the safe limit or the overspeed protection logic has failed its self-test. In either case, it signals a non-normal condition that could trigger protective action, such as shutdown, if not addressed. It is not a normal indication of starting, nor is it related to oil temperature or the start valve status. Those conditions would be indicated by different indicators.